This disclosure is directed to polyetherimide compositions, and in particular to electrical tracking resistant polyetherimide compositions, articles formed therefrom, and their methods of manufacture.
Polyetherimides are known as outstanding high performance materials, having a high glass transition temperature (Tg), high modulus, and strength at elevated temperatures, as well as excellent chemical resistance. They are useful in the manufacture of articles and components for a wide range of applications. Because of their broad use, particularly in the electrical and electronic industries, it is desirable to provide polyetherimides with good electrical tracking resistance. Electrical tracking is the formation of conductive pathways on the surface of a polymer under certain conditions and at a certain voltage. Electrical tracking in a polymer can be a source of fire in parts therefore resistance to electrical tracking is often an important safety requirement for a material used in certain electrical applications. A common method of reporting the electrical tracking resistance of a polymer is by its comparative tracking index rating (CTI). Currently known polyetherimides can have a comparative tracking index (CTI) of 100 to 175 volts. However, some applications can require a material having a higher CTI.
There accordingly remains a need in the art for polyetherimide compositions that have excellent electrical tracking resistance. It would be a further advantage if the compositions could be rendered electrical tracking resistant without a significant detrimental effect on one or more of material cost, processability, and mechanical properties.